The objective of this grant is to identify the active principle responsible for an anti-asthmatic activity discovered in the resin of the red cedar tree. Cedar had been used as an anti-asthmatic folk remedy in rural Cuba for many generations before Dr. Rene M. Mora, a Cuban physician, began using the resin preparation with remarkable success. The anecdotal data offered in this report are now corroborated by results of preliminary experiments in two animal models. In Ascaris-sensitive sheep, the increase in specific lung resistance that one normally observes in response to an aerosol of A. suum is reduced significantly by one five-week treatment with Asthmacedar. In ovalbumin-sensitized guinea pigs, the contractive response resulting from antigen exposure is mitigated both by the feeding of cedar resin to the guinea pigs for several weeks and by direct incubation of the strips with the preparation. In the guinea pig system, the cedar resin appears not to be an anti-histamine or anti-leukotriene, but rather to be acting through another mechanism. None of the human or animal subjects to whom this drug has been administered have revealed any signs of toxicity. The relative speed and economy of the in vitro guinea pig bioassay makes feasible the proposal to fractionate and identify the active component in the cedar resin.